Categories In Grunge Template have broken links

Hi

I’m using Grunge template (guitar pic in header). I have added categories and added posts to them. The categories are visible in the side bar but when I click on any of them I get an “oops broken link” message from Google. All the posts are on the home page.

Can anyone tell me what I need to do to fix this problem.

Also how can I show only a part of a post with read more of this article link at the bottom of the partial post?

https://www.learnbluesguitaronline.net

I hope someone can help

Regards

Loran888